Polymers of cycloolefins containing a norbornene moiety are well-known. Such polymers can be prepared by ring-opening polymerisation of monomers in the presence of a metathesis catalyst system. Ring-opening metathesis polymerisation (hereinafter referred to as ROMP) results in a thermoset network. By thermoset network the skilled person understands a 3 dimensional polymer structure.
Thermoset polymers usually bond on themselves, but require a surface preparation to obtain optimal structural bonding, typically sanding, sandblasting or using peel ply fabric. Solvent wipe is not active enough.
Thermoset polymers prepared from norbornene-type cycloolefin monomers using W or Mo based catalysts, however, do not bond on themselves like the other thermoset polymers, even when preparing the surface by sanding, sand-blasting or using peel ply fabric.
In order to bond together two norbornene-type polycycloolefin systems, an adhesive is required, the use of which is disadvantageous in that it has usually not the same properties as the thermoset network prepared from the norbornene-type cycloolefin monomers using ROMP as polymerisation mechanism.
For example, in view of the difference in thermal expansion between the adhesive and the parts of the network assembly, bonding lines can be observed at the surface of the network assembly which gives the final product a poor optical appearance.
As another example, the adhesive used to bond together the parts of the network assembly has not the same chemical resistance as the thermoset network so that there occurs the problem that the parts of the network assembly become separated again when the final product is exposed to a harsh chemical environment.
WO 97/38036 describes a metathesisable composition that includes a mixture of a thermal carbene-free ruthenium catalyst and a thermal ruthenium carbene catalyst. The polymers resulting from the metathesis polymerisation are said to be suitable “as adhesives for bonding substrates having low surface energies (for example Teflon, polyethylene, polypropylene).” The compositions disclosed in WO 97/38036 are also said to be useful as “thermally curable adhesives” and as protective coatings on substrates. However, there is no example of a specific adhesive or coating formulation.
WO 03/000764 A2 relates to an adhesive or coating composition prepared by mixing together at least one metathesisable highly-reactive cycloolefin (for example a norbornadiene) and a metathesis catalyst. Another embodiment described therein is a two-part adhesive or coating system wherein the first part includes at least one first metathesisable material, and the second part includes at least one liquid metathesis oligomer or polymer and a metathesis catalyst.
Thus, it is the problem underlying the present invention to provide a polycycloolefin network assembly which avoids the use of an adhesive to bond together thermoset networks prepared from norbornene-type cycloolefin monomers.